One example of a conventional mechanical two-way loudspeaker is shown in FIG. 1. A conical diaphragm 4" for the low frequency range (hereinafter referred to as the low frequency diaphragm) is fixedly secured through an edge 3 to the mounting edge 2A of a frame 2 fixedly mounted on a magnetic circuit 1. A diaphragm 5 for the high frequency range (hereinafter referred to as the high frequency diaphragm) is fixedly secured through an edge 6 to the low frequency diaphragm 4" in such a manner that the diaphragms 4" and 5 are coaxial with one other. A voice coil bobbin 7 fixedly secured to the inner peripheral edges of the low frequency diaphragm 4" and the high frequency diaphragm 5, and a voice coil 8 wound on the voice coil bobbin 7 are inserted into the magnetic gap 1A of the magnetic circuit 1. In FIG. 1, reference numeral 10 designates a damper which supports the voice coil bobbin 7.
When a current bearing sound signals flows in the voice coil 8 in the magnetic gap 1A of the magnetic circuit 1, it is vibrated in response to the sound current according to Fleming's left-hand rule, so that the high frequency diaphragm 5 and the low frequency diaphragm 4" are operated sharing the vibration; more specifically, in the high frequency range, the low frequency diaphragm 4" is not sufficiently vibrated, while the high frequency diaphragm 5 is primarily vibrated, and in the low frequency range both the low frequency diaphragm 4" and the high frequency diaphragm 5 are vibrated. This is a specific feature of the conventional loudspeaker.
However, in the above-described conventional mechanical two-way loudspeaker, the sound pressure from the low frequency diaphragm 4" which is conical and provided behind the high frequency diaphragm 5, interferes with the sound pressure vs. frequency characteristic of the high frequency diaphragm 5 during vibration, as a result of which this characteristic is not flat, as is desired.